The present invention relates to a radial field electromagnetic flow meter. The "radial field electromagnetic flow meter" is defined herein as an electromagnetic flow meter which comprises: a linear fluid passage for allowing an electrically conductive fluid to flow therethrough, having an annular cross-section and being surrounded by electrically insulating surfaces; a radial field generator for generating magnetic flux over the entire circumference in a space including a cross-section of the fluid passage in radial directions with respect to the center line of the space; a separating plate made of non-magnetic material, extended along at least a part of the radial magnetic flux, and projected into the fluid passage in parallel with the center line, the surfaces of both sides of the separating plate being electrically insulated from each other; and a pair of electrodes disposed in the foregoing space of the radial magnetic flux respectively, at portions close to mutually opposite ends of an angular range not including the separating plate; whereby a signal voltage proportional to the flow rate of the fluid to be measured is generated on the basis of an electromotive force induced across the pair of electrodes due to the movement of the electrically conductive fluid across the radial magnetic flux.
As prior art of such a radial field electromagnetic flow meter, there are those disclosed in Japanese Pat. Publication No. 56-54565, and U.S. Pat. No. 3,911,742. The magnetic circuit of the radial field generator used in these radial field electromagnetic flow meters is arranged so that none of its parts are made of ferromagnetic material with the exception of a magnet device having north and south magnetic poles arranged along the center line of the fluid passage.
In the conventional radial field electromagnetic flow meter described above, the magnetic circuit of the radial magnetic flux generator does not have any parts made of ferromagnetic material with the exception of the magnet device, so a disadvantage has existed in prior devices that the magnetic reluctance is a large amount and large energy is required to obtain the sufficient magnetic flux density required by the radial magnetic field.